Preparation and application of Hafnium oxide

Hafnium oxide, HfO2, specific gravity 9.68. Melting point 2,758±25℃. Boiling point 5,400 ℃. The monoclinic hafnium dioxide is transformed into the tetragonal system in a sufficient oxygen atmosphere at 1,475-1,600°C. Insoluble in water and general inorganic acids, but slowly soluble in hydrofluoric acid. It reacts with hot concentrated sulfuric acid or acid sulfate to form hafnium sulfate [Hf(SO4)2], which is mixed with carbon and then heated through chlorine to generate hafnium tetrachloride (HfCl4), and it reacts with potassium fluorosilicate to generate potassium fluorohafnium (HfCl4). K2HfF6), which acts with carbon above 1,500 °C to form hafnium carbide HfC. It is prepared by direct high temperature firing of hafnium carbides, tetrachlorides, sulfides, borides, nitrides or hydrated oxides.

Application

Hafnium oxide can be used as a high temperature resistant material.

1) Prepare a hafnium oxide dielectric film.

2) A homogenous double-layer hafnium oxide antireflection film is prepared, which belongs to the technical field of optical thin films.

3) Preparation of a germanium oxide and hafnium oxide hybrid aerogel composite material, the method includes impregnating the prepared hybrid sol into the treated inorganic fiber material, after gelation, sufficient aging, and then supercritical The hybrid aerogel composite material was obtained by drying.

Preparation

(1) Prepare qualified hafnium sulfate feed solution:

Taking hafnium oxide as the raw material, it is successively subjected to alkali melting, hydrochloric acid dissolution, crystallization, impurity removal, precipitation, filtration, and drying, and then dissolved in a sulfuric acid solution with a H concentration of 9 mol/L, and the H concentration in the hafnium sulfate feed solution is adjusted to 2.5 mol /L, the HfO2 concentration is 50g/L, and the volume of the hafnium sulfate feed solution is 15 liters;

(2) The extractant is made of industrial-grade N235 compounded with industrial-grade A1416 and industrial-grade sulfonated kerosene. The components of the extractant are as follows: N235: 20%, A1416: 7%, sulfonated kerosene: 73%, Adopt the above-mentioned extraction agent to carry out three-stage extraction, separate the zirconium and hafnium in the hafnium sulfate feed liquid, and obtain the low-zirconium hafnium sulfate extraction residual liquid, which is as follows: Acidify, mix with the hafnium sulfate feed liquid in step (1) again for 30 minutes, carry out first-level extraction, separate organic phase and water phase after layering, water phase is directly used for next-level extraction treatment, and organic phase is processed by two-stage extraction. In back extraction, the two-stage organic phase is regenerated to obtain a regenerated organic phase, and the regenerated organic phase is subjected to two-stage acidification and then used for the next-stage extraction operation. This is repeated for three extractions.

The low-zirconium hafnium sulfate extraction residue after three-stage extraction is successively subjected to ammonia precipitation, rinsing, drying, hydrochloric acid leaching, crystallization purification, ammonia precipitation, rinsing, drying, and calcination to obtain high-purity low-zirconium hafnium oxide products.